IIT JEE Revision Alkanes Physical Properties

1. State: CH4 to C4H10 are gases, C5H12 to C17H36 are liquids and higher ones are solids
2. Boiling point: Boiling point increases with molecular mass(carbon atoms).
Branched isomers have a lower boiling point than normal alkanes.
3. Melting point: Melting points increase with molecular mass. But the increase is not a regular variation. In general, the alkanes with even number of carbon atoms have a higher melting points as compared to the immediately next lower alkanes with odd number of carbon atoms.
4. Solubility: Alkanes are almost non-polar molecules. Being nonpolar, these are insoluble in water. They dissolve in non-polar solvents such as ether, benzene, carbon tetrachloride etc. The solubility generally decreases with increase in molecular mass.
5. Density: Liquid alkanes lighter than water. the density increases with the increase in the number of carbon atoms.